Continuous tube-rolling process and apparatus therefor.



R. 0. S'I'IEFEL. CONTINUOUS TUBE ROLLING rnoosss AND APPARATUS THEREFOR.

APPLICATION PILED MAE. 1S, 1912,

Patented Mar. 11,1913.

8 SHEETS-BREEZE 1.

@371 #13 abtozneus R. G. STIEFEL.

CONTINUOUS TUBE ROLLING PROOESS AND APPARATUS THEREFOR. APYLIOATION FILED MAR.13, 1912.

1,055,368, I Patented Mar. 11, 1913.

3 BHBETiF-BHEET 2.

. gwvehfoz fi mhllgelth azu R. C. STIEFBL. CONTINUOUS TUBE ROLLING PROCESS AND APPARATUS THEREFOR APPLICATION FILED MAR.13, 1912.

1 055 363 Patented Mar. 11,1913.

8 SHEETS-BEBE! 3.

war/ 35 6: l Snvem/Coz W V 35137718 GHQ wings W wnmdm RALPH CHARLES STIEFEL, OF ELLWOOD CITY, PENNSYLVANIA.

CONTINUOUS TUBE-ROLLING PROCESS AND APPARATUS THEREFOR.

Specification of Letters Patent.

Patented Mar. 11, 1913.

Application filed March 13 1912. Serial No. 683,540.

To (all whom, H llltlj/ concern.

I in eti'ect to act ninety degrees apart in relic it known that l. ltailru (juxunns i spot-t to the metal of the billet or tube. Even S'rinrnn. a citizen of the lhutcd States, 1 with these provisions, in such processes the and resident of Ellwood City, lemisylvania. have invented certain new and useful improvements in Continuous 'lube-llolling Processes and Apparatus 'llieret'mr, of which the following is a specification, accompanied by drawings.

The invention relates primarily to the cross rolling of steel and other tubes and tubular billets in a heated state in the manufacture of seamless tubes. I

The objects of the invention in its most 15 complete and preferred embodiment are to accomplish by cross rolling rapidly and easily the elongation of the tube or billet and the reduction of its wall thickness, doing this in such a manner that the process shall be independent of specially designed apparatus or grooved rolls for each considerable difference in size of tube to be 'made, and in such a manner that the friction and wear and tear on the mandrel bar and rolls shall be slight as compared with longitudinal rolling processes employing grooved rolls which circumferentially embrace the tube.

It has heretoftnbeen a conunon' practice in the rolling of seamless tubes in continuous rolling mills to'roll the tubes longitudinally between a plurality of successive sets of grooved rolls having grooves which form a circular or elliptical pass and embrace the billet or tube circumfcrentially for the greater portion of its circumference and which roll the billet or tube longitudinally on the mandrel bar, elongating and stretch ing the metal, causing it to grip the mandrel bar so tightly that. special devices are frequently necessary for loosening the billet upon the mandrel bar before it is stripped therefrom. If the roll axes of such grooved rolls are perpendicular to the axis of the pass, neighboring pairs of rolls are usually placed at right angles, so as to act at ninety degrees or a quarter turn on the billet and not all to act along the same sides of the billet, but in lieu of this the pairs of rolls are sometimes slightly inclined or skewed, so as to give a quarter turn to the billet itself in passing between neighboring pairs of rolls and allow the roll pairs to be all conveniently placed in like positions relativelv to the'pass, the quarter turning of the billetor tube causing the successive rolls flow of the metal and the rolling action is necessarily different at different points in the circumference of the billet, whereas in the cross rolling process such is obviously not the case. Moreover the process of longitudinal rolling in grooved rolls necessitates ditlercnt sets of rolls with different sizes of grooves for every considerable difference in the diameter of the tubes rolled with consequentloss of time and increase of expense in changing the rolls.

Under the present im n'ovement, the billet is subjected to cross rolling action between successive pairs of cross rolling bodies, which treat the billet alike upon all sides; and preferably I also simultaneously subject the metal to a longitudinal tensionwvhile so cross rolling it,"'and I do the rolling between rolling'faces which are preferably short and convex longitudinally of the pass and cause the metal to yield and flow out beneath them longitudinally, and preferably at or toward the rear end of the series of rolls, I subject the billet to cross rolling between rolls which have rolling faces which are flat in the longitudinal direction and are approximately parallel with the pass and which smooth the billet or tube and also slightly enlarge it upon the mandrel bar.

In the drawings, Figure 1 is a diagrammatic longitudinal sectional view. of one preferred arrangement of rolling bodies for carrying out the present invention, Fig. 2 is a diagram of the same arrangement of rolling bodies in elevation, showing the circles corresponding to the central lines or mean diameters of the rolling contact surfaces of the rolls and showing the directions and speeds of the rolling motion and the transverse and longitudinal speed c0mponents of the same, Fig. 3 shows in plan view a modified arrangement of rolls for carrying out the invention, Fig. 4 is a cor responding diagran'i of the mean diameter circles thereof 1n elevation, Fig. 5 shows an elevation of another type and arrangement of the rolls for operating the process, Fig. 6 shows in plan view, four of the roll pairs of Fig. 5, and Fig. 7 is a section through a pair of disk rolls, presenting angular convex faces, instead of curved convex faces, to the pass. A

The roll bearings, housings, guides for .the' billet, driving connections and other parts not necessary te theunderstanding of the invention are omitted for clearness from the drawings.

In Figs. 1 and 2, the rolling bodies are four pairs of overlapped disk-shaped rolls, having horizontal axes raised above the plane of the axis of the pass, so as to give a feeding effect in addition to the cross rolling action, as well understood. The axes of each pair are parallel and the faces of the rolls overlapped. The rolls are slightly but sufficiently inclined to the axis of the pass in order to allow clearance, for the billet or tube. The rear portion of roll A acts opposite the forward portion of roll B, and the other pairs of rolls C, D and E, F and G, H are overlapped to act similarly.

For convenience in explaining the process, the section for each roll in Fig. 1 is taken, as follows: The roll A is sectioned .horizontally from its axis toward the lefthand side in the plane of the axis 34, Fig. 2.

On the active side, or righthand side, of the axis the section plane runs from the axis through the central point. of the surface of contact at the instant between the roll and the billet, as shown by the section line 45 in Fig. 2. Similarly, the other rolls are each sectioned, one half horizontally, and the other half through .the inclined plane passing through the axis and the central point of the surface in contact with the billet. This gives the slightly onesided appearance to the sections which may be noticed in Fig. 1. Circles a, Z). (1, (Z, c, f, g, h in Fig. 2 are paths of the motion of revolution of those points in the faces of the respective rolls which pass through the centers of the surface in contact with the billet. Consequently, the speed and direction of motion and the approximate longitudinal and cross effect of the roll upon the billet may be graphically determined from these circles, which correspond to the mean working diameters of the working or contact sur faces. The correction for the slight obliquity of the roll axes may be neglected. The arrows 011 these circles show the direction of rotation. The axial line through the pass is marked A portion of the mandrel bar is shown at J. and the billetor tube at K. The first pair of disk rolls, A. B, give the least feeding effect, because their axes are least raised above the axis of the pass, as shown by the height of the line 3--1- in Fig. 2 above the axis of the pass.

Let the tangent'my) be drawn through the center of contact 722 of the disk on the billet and of length and direction corresponding to the speed of the roll surface at that point. Let lines m7 and mr be drawn to rolling, determined by the degree of raising i the axis of the roll, should be small, as is shown. The contact surfaces of the rolls should be convex and short longitudinally of the pass, so that they roll transverse and slightly oblique spirally overlapping depres-. sious or shallow grooves in the surface of the heated billet, and facilitate the spreading and flow of the metal longitudinally from beneath the rolling surfaces, so as to elongate the billet upon the mandrel bar and reduce its wall thickness. The succeeding pair of rolls, C, D, which act progressively and simultaneously with the rolls A, B, upon the billet during the greater portion of its length, may be of the same shape, but with preferably slightly less convexity, so as to span and not fit the previously made spiral grooves. The cross rolling component of motion of the rolls C, D, may be made less than that of the preceding rolls by an amount proportional to the differing the metal without twisting it. Twist, however, may be imparted in making tubes for special uses, by varying the cross rolling components.

The longitudinal component on r. is increased preferably by an amount sufiiciently in excess of that corresponding to the elongation of the tube by these rolls to produce a longitudinal tension upon thebillet between theserolls and the preceding pair. This tension or pulling on the billet not only lessens the tendency of the billet to be expanded or enlarged upon the mandrel by the cross rolling, but also assists the receding pair of rolls in elongating the bi let. It will be understood that the longitudinal or feed component of the speed depends on both the roll speed and the angle corresponding with 79' m g and that an increase of either the roll speed or the angle will give an increase of the feed component. Simi larly, several succeeding pairs of rolls mayv be used, with the same or varying cross rolling speed and with increasing longitudinal feed component, and preferably with increasing length and decreasing curvature of the convex rolling surface, and, ofcourse, diminishing widthof pass corresponding to the desired reduction of thickness and diameter of the tube. i

It will be seen, as shown in Fig. 1, that a pair of shallow spiral depressions or grooves are rolled in the billet or tube by each of the succeeding roll pairs except by the last. The last pair, G, H, have the greater portions of their workingfaces substantially flat and parallel with the pass, as viewed in cross section along the pass. Between these last rolls therefore, the metal is subjected to cross rolling with but little opportunity and tendency to flow longitudinally from beneath the fiat and relatively wide faces, tlie wavy or grooved surface is stead of requiring, as in the case of grooved rolls, a change of the rolls themselves. It will also be seen that by successively diminishing the convexity of the rolling surfaces, the tendency of the rolls to fit into the spiral groove, made by the previous rolls 1s lessened. Instead of curved convex working faces, substantially straight line components, forming a V-shaped section, as illustrated in Fig. 7 and giving an angular form of convexity, may be used, and I use the term convex to include angular forms. In either form the pass between the two rolls of the pair is rapidly convergent and then rapidly divergent in order to aid in forcing the metal to flow endwise.

Although it is preferable to effect the cross rolling by means of rolling surfaces which are both convex and short longitudinally of the pass and which give progressively greater feeding action and produce the pulling or tension in the billet, nevertheless it is possible, for example, to use convex faces of very considerable length along the pass or to use faces that are narrow or short in the direction of the pass with very little or no degree of convexity, but in such cases the tendency to expand the tube is relatively greater and the elongating effect of ,the rolls even with great pulling action due to increasing feeds is lessened. The successive roll pairs are placed as close to each other as convenient, in order that they may. act simultaneously on the billet for a longer port-ion of itslength than if they were farther apart. Manifestly, a greater or less number of roll pairs than that shown may be employed, but I prefer to use at least three or more pairs besides the last, or smoothing rolls, making at least four pairs, as shown.

In the process just described. it will be seen that the tubular billet while in the.

heated state upon a mandrel bar is subjected simultaneously to cross rolling pressure in a manner to spread out the metal cndwise from beneath the convex rolling surface. and to a simultaneous pulling or tensile stress longitudinally. \Vhere the pulling or tensile stress 18 not employed. the cross rollingtends to loosen and to enlarge the tube upon the mandrel, but by combining the cross rolling and the ulling with a mod erate reduction of wall. thickness between each roll pair, the tube may be kept substantially circular and just loose enough upon the mandrel bar to facilitate its elongation thereupon. In addition to the other advantages, the wear and tear upon the mandrel bar is greatly reduced by this process as compared, for-example, with longitudinal rolling where the bar is very tightly embraced by the tube and therefore heats more rapidly.

The process is in no'wise limited to the arrangement of apparatus shown in Fig. 1. Thus, in Figs. 3 and 4, there are illustrated opposed pairs of disk-shaped rolls, the rolls of each revolving in opposite directions and placed opposite each other, as shown, instead of being overlapped, as in Fig. 1. As will be understood, the feeding etfect in this case is produced between such disk rolls by raising of one and lowering of the opposite roll, as plainly shown in Fig. 4, where the circles corresponding to the mean diameters of the working faces of the respective, rolls are shown. In 1 and 2, the smaller diameter of one roll is opposed to the larger diameter of the opposite roll. In Figs. 3 and 4c, the larger diameters of each roll pair are opposed to each other, which conse-- quent-ly produmrs a tendency to twist the metal of the billet while between a pair of rolls. In Figs. 1 and 2, the rolls a'll revolve in like direction and feed by reason of their axial elevation above the axis of the pass. Obviously all or any paircould be below the axis and revolve'in the oppo site direction. In Figs. 5 and 6, barrelshaped rolls with crossed axes are illustrated, arranged to give approximately the same cross rolling and feed components as in Fig. 1. The first rolls, A", B",-have the greatest degree of convexity, as before. The intermediate rolls are of decreasing convexity. while the smoothing and loosening rolls, G", H, in order to'give a substantially flat contact surface in the longitudinal dircction, have a slightly concave hyperboloidal curve. In cases where it is not necessary that the tube be made substan- 115 tially smooth and'even by the last rolls, the convex-faced rolls may be the last rolls used.

It will be seen that the improved process will not be materially interfered with by even a considerable wearing away of the 120 rolling surfaces of the disks or rolls employed in carrying it out, although corresponding Wear upon grooved rolls for a longitudinal rolling process would be prohibitive of their further use. So there are many 185, other incidental advantages that arise, directly or indirectly, from the improved process in addition to its prime advantage and importance in giving a more uniform and better treatment to the tube or billet. 180

I employ the terms billet and tube interchangeablyto include the-tubular billet or tube at anypart of its manufacture-.=

1. In a processot rolling tubes the improvement which-i comprises subjecting a tu-' bular billet to cross rolling action on a mandrel bar simultaneously and progressively between a plurality of pairs of cross rolling bodies and at the same time subjecting the billet to progressively increasing feeding components of movement of the rolling surfaces, the length of contact of the cross rolling bodies being so grestricted that themetalflows mainly longitudinally, elongating the tube upon the'mandrel, and subjecting the 7 metal to a stretching action while so being bodies and at the same timesubjecting the billet to progressively increasing feeding components of movement of the rolling surfaces, the length of contact of the cross rolling bodies being so restricted that the metal flows mainly longitudinally, elongating the tube upon the mandrel, and toward the-exit endoftlie pass subjecting the billet to cross rolling pressure between bodies having relatively long and substantially flat faces longitudinally and thereby smoothing the billet.

3. In a process of rolling tubes the improvement which comprises subjecting a tubular billet to cross rolling action on a mandrel bar simultaneously and progressively between a plurality of pairs of cross-rolling bodies and at the same time subjecting the billet to progressively increasing feeding components of movement of the rolling surfaces, the length of contact of the cross rolling bodies being so restricted that the metal flows mainly longitudinally, elongating the tube upon the mandrel.

4. Improvement in processes for rolling tubes which comprises cross rolling and elongating a tubular billet on a mandrel bar simultaneously between a plurality of pairs of cross rolling bodies acting obliquely on the billet and thereby rotatin and advancing the billet and mandrel, and simultaneously subjecting the billet to a longitudinal tension in the interval between two sucrtubes which comprises cross rolling and ceeding roll pairs.

5. Improvement n processes for rolling elongating a tubular .billet on a mandrel bar simultaneously between a plurality of pairs of cross rolling bodies acting obliquely on the billet and thereby rotating and advancingthe billet i-aiid mandrel, and progressivelylncrfiising the -longitudinal feeding actionfof 'su-ceeding pairs of bodies without 1 the'incre'ase of crosswise act-ion.--=

6. Improvement in processes for rolling tubes which comprises cross rolling and elongating a tubular billet on a mandrel bar simultaneously between a plurality of roll 1 pairs, and restricting the expanding effect of one or more of the roll pairs by increasing the feeding effect of the. succeeding pair in excess of that corresponding to the elongation of the billet, thereby producing a lon gitudinal stress in the billet.

V 7. Improvement in processes for rolling tubes which comprises cross rolling and elongating a tubular billet on a--mandrel bar simultaneously between a plurality of roll .pairs', and restricting the expanding effect of one or more of the roll pair's by increasing the feeding effect'of the succeeding pair in excess of that corresponding to the elongation of the billet, thereby producing a longitudinal stress in the billet, and later in the progress smoothing the tube between substantially parallel cross'rolling surfaces.

8. Improvement in the art of rolling and elongating tubes which comprises subjecting i a tubular billet to cross rolling on a mandrel bar between a plurality of'pairs of oblique- .acting cross rolling surfaces which are convex but are progressively flatter and longer longitudinally of the pass.

9. Improvement in the art of rolling tubes, whichcomprises subjecting a tubular billet to cross rolling action on a mandrel bar simultaneously and progressively between a plurality ofpairs of cross rolling bodies, the length of contact of the cross rollingbodies upon the billet being so restricted in longitudinal direction that the metal flows or is forced out mainly longitudinall elongating the tube upon the mandrel, an toward the exit end of the pass further subjecting the billet to cross-rolling pressure on contact areas that are-relatively long and substa'ntially flat longitudinally ofthe billet,

thereby smooth-ing the billet.

10. Improvement in the art of rolling tubes which comprises cross rolling a tubular billet on a mandrel bar progressively and simultaneously at a plurality of different portions of its length between a plurality of pairs of rolling bodies andcausing longitudinal flow and relatively great elongation of the billet in the earlier roll pairs by rolling surfaces making contact areas relatively narrow and convex longitudinally, one of the later roll pairs making contact areas relatively flat longitudinally, forming an approximately parallel-sided pass.

11. Improvement in continuousmills for rolling tubes comprising a plurality of coactmg pairs of cross rolling rolls, one or more of the earlier roll pairs having rolling surfaces convex and relatively short in the longitudinal direction of the pass, and one of the succeeding roll pairs having rolling surfaces relatively 1on and substantially flat in the longitudinal direction of the pass.

12. Improvement in apparatus for elongating tubes and billets by cross rolling, comprising a plurality of separate successive pairs of cross rolling rolls having convex rolling faces, the directions of the rolling motion of successive pairs at their points of contact with the billet being progressively and substantially more inclined to a plane perpendicular to the axis of the pass, and the endwise or feeding components of the -motion being progressively increased, whereby the endwise components of the rolling motion and also the ratip of the endwise components to the crosswise components of the motion are increased progressively in the successive roll pairs.

13. Improvement in ap aratus for elongating tubes and billets y cross rolling, comprising a plurality of separate successive pairs of cross rolling rolls said rolls being disk-shaped rolls set with their axes substantially crosswise to the axis of the ass with progressively increasing eccentricities of the rolls, that is to say, increasing distances between the axes of the rolls and the axis ofthe pass where they cross In testimony whereof I have signed this specification in the presence of two subscribing witnesses this 8th day of March, 1912.

RALPH CHARLES STIEFEL. Witnesses: 1

HAROLD BINNEY,

Auousrx PSCHTERER. 

